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SQLSREVER如何创建和使用动态游标

▲创建游标

CREATE PROCEDURE Usp_CreateCursor(@Select_Command varchar(8000),@Cursor_Return CURSOR VARYING OUTPUT) AS
/*存储过程名称:Usp_CreateCursor
功能描述:    根据指定的SELECT创建一个动态游标
参数描述:    @Select_Command ---SELECT语句;@Cursor_Return ---要返回的游标变量
思路:        动态游标的关键是不知如何去构造它的SELECT语句,因为SELECT是个字符串表量,定义时不能直接用它,但它可以来源于表。
所以我的目的就是创建一个统一的表,从中取数据不就可以了。建表有一定的语法规则,所以就应该根据栏位列表生成相应的
格式,这个可以从系统表中获取。关键的问题是如何将数据插入到临时表,我摸索出一条语句可
实现这个功能,那就是INSERT INTO <TABLE_NAME> EXECUTE <SQL>,而SQL7.0的帮助未讲。有表有数据就可以创建了。
创建人:      康剑民
创建日期:    2001-07-11
*/
Declare @Select_Command_Temp Varchar(8000), ---存放SELECT临时语法
@Table_List varchar(255), ---存放表的列表
@Column_List varchar(8000),---存放栏位列表
@Table_Name varchar(30),---存放单独表名
@Column_Name varchar(30),---存放单独栏位名(但有可能是*)
@Column_Syntax varchar(8000),---存放栏位建表时的语法(综合)
@Column_Name_Temp varchar(30),---存放栏位名称
@Column_Type_Temp varchar(30),----存放栏位类型
@Column_Syntax_Temp varchar(8000),---存放栏位建表时的语法(单个)
@Column_Length_Temp int,---存放栏位长度
@Column_Xprec_Temp int,---存放栏位精度
@Column_Xscale_Temp int,---存放栏位小数位数
@From_Pos int,---存放from的位置
@Where_Pos int,---存放where的位置
@Having_Pos int,---存放having的位置
@Groupby_Pos int,---存放groupby的位置
@Orderby_Pos int,---存放orderby的位置
@Temp_Pos int,---临时变量
@Column_Count int,---存放栏位总数
@Loop_Seq int---循环步进变量

---创建临时表
Create Table #Test(a int)
---如果传来的SELECT语句不是以'select'开头,自动修改
If Left(Lower(Ltrim(@Select_Command)),6) <> 'select' Select @Select_Command = 'Select ' + @Select_Command
---将开头‘SELECT’去掉
Select @Select_Command_Temp = Lower(Ltrim(@Select_Command))
If Left(@Select_Command_Temp,6) = 'select' Select @Select_Command_Temp = Right(@Select_Command_Temp,Len(@Select_Command_Temp) - 7)
---取各保留字位置,以便获得表的列表
Select @From_Pos = CHARINDEX(' from ',@Select_Command_Temp)
Select @Where_Pos = CHARINDEX(' where ',@Select_Command_Temp)
Select @Having_Pos = CHARINDEX(' having ',@Select_Command_Temp)
Select @Groupby_Pos = CHARINDEX(' groupby ',@Select_Command_Temp)
Select @Orderby_Pos = CHARINDEX(' orderby ',@Select_Command_Temp)

If @Where_Pos > 0 Select @Temp_Pos = @Where_Pos
If @Having_Pos > 0 And @Having_Pos < @Temp_Pos Select @Temp_Pos = @Having_Pos
If @Groupby_Pos > 0 And @Groupby_Pos < @Temp_Pos Select @Temp_Pos = @Groupby_Pos
If @Orderby_Pos > 0 And @Orderby_Pos < @Temp_Pos Select @Temp_Pos = @Orderby_Pos
---取表列表
If @Temp_Pos > 0
Begin
Select @Table_List = SUBSTRING(@Select_Command_Temp,@From_Pos + 6 ,@Temp_Pos - @From_Pos - 1)
End
Else
Begin
Select @Table_List = SUBSTRING(@Select_Command_Temp,@From_Pos + 6 ,Len(@Select_Command_Temp) - @From_Pos - 1)
End

Select @Column_Syntax = '
---只列出栏位
Select @Select_Command_Temp = Left(@Select_Command_Temp,@From_Pos - 1)
While Len(@Select_Command_Temp) > 0
Begin
---取逗号位置
Select @Temp_Pos = CHARINDEX(',',@Select_Command_Temp)
---初次取栏位名称
If @Temp_Pos > 0
Begin
Select @Column_Name = Left(@Select_Command_Temp,@Temp_Pos - 1)
End
Else
Begin
Select @Column_Name = @Select_Command_Temp
End
---取表名和栏位名(可能是‘*’)
If CHARINDEX('.',@Column_Name) > 0
Begin
Select @Table_Name = Left(@Column_Name,CHARINDEX('.',@Column_Name) - 1)
Select @Column_Name = Right(@Column_Name,Len(@Column_Name) - CHARINDEX('.',@Column_Name))
End
Else
Begin
Select @Table_Name = @Table_List
End

---栏位出现'*'
If CHARINDEX('*',@Column_Name) > 0
Begin
Select @Column_Name = '
Select @Loop_Seq = 1
---取栏位个数
Select @Column_Count = Count(*)
From SysColumns
Where Id = Object_Id(@Table_name)
While @Loop_Seq <= @Column_Count
Begin
---取栏位名称,栏位类型,长度,精度,小数位
Select @Column_Name_Temp = SysColumns.Name,
@Column_Type_Temp = Lower(SysTypes.Name),
@Column_Length_Temp = SysColumns.Length,
@Column_Xprec_Temp = SysColumns.Xprec,
@Column_Xscale_Temp = SysColumns.Xscale
From SysColumns,SysTypes
Where SysColumns.Id = Object_Id(@Table_name) And
SysColumns.Colid = @Loop_Seq And
SysColumns.XuserType = SysTypes.XuserType
---形成栏位语法表达式
Select @Column_Syntax_Temp = Case When @Column_Type_Temp In ('datetime','image','int') Then @Column_Name_Temp + ' ' + @Column_Type_Temp
When @Column_Type_Temp In ('binary','bit','char','varchar') Then @Column_Name_Temp + ' ' + @Column_Type_Temp + '('+Convert(Varchar(10),@Column_Length_Temp) + ')'
Else @Column_Name_Temp + ' ' + @Column_Type_Temp + '('+Convert(varchar(10),@Column_Xprec_Temp) + ',' + Convert(varchar(10),@Column_Xscale_Temp) + ')'
End
Select @Column_Syntax = @Column_Syntax + @Column_Syntax_Temp + ','
Select @Loop_Seq = @loop_Seq + 1
End
End
Else
Begin
---取栏位名称
Select @Column_Name_Temp = @Column_Name
---取栏位类型,长度,精度,小数位
Select @Column_Type_Temp = Lower(SysTypes.Name),
@Column_Length_Temp = Isnull(SysColumns.Length,0),
@Column_Xprec_Temp = Isnull(SysColumns.Xprec,0),
@Column_Xscale_Temp = Isnull(SysColumns.Xscale,0)
From SysColumns,SysTypes
Where SysColumns.Id = Object_Id(@Table_name) And
SysColumns.Name = @Column_Name_Temp And
SysColumns.XuserType = SysTypes.XuserType
---形成栏位语法表达式
Select @Column_Syntax_Temp = Case When @Column_Type_Temp In ('datetime','image','int') Then @Column_Name_Temp + ' ' + @Column_Type_Temp
When @Column_Type_Temp In ('binary','bit','char','varchar') Then @Column_Name_Temp + ' ' + @Column_Type_Temp + '('+Convert(Varchar(10),@Column_Length_Temp) + ')'
Else @Column_Name_Temp + ' ' + @Column_Type_Temp + '('+Convert(varchar(10),@Column_Xprec_Temp) + ',' + Convert(varchar(10),@Column_Xscale_Temp) + ')'
End
Select @Column_Syntax = @Column_Syntax + @Column_Syntax_Temp + ','

End
---处理栏位列表
If @Temp_Pos > 0
Begin
Select @Select_Command_Temp = Right(@Select_Command_Temp,Len(@Select_Command_Temp) - @Temp_Pos)
End
Else
Begin
Select @Select_Command_Temp = '
End
End
---形成正确的栏位创建语法
Select @Column_Syntax = Left(@Column_Syntax,Len(@Column_Syntax) - 1)
---修改临时表的结构
Execute('Alter Table #Test Add )
Execute('Alter Table #Test Drop Column a')
---将SELECT执行的结构集插入到临时表
Insert Into #Test
Execute(@Select_Command)
---创建游标
Set @Cursor_Return =  CURSOR LOCAL SCROLL READ_ONLY FOR
Select *
From #Test
---打开游标
Open @Cursor_Return

 

▲使用游标

/注:在SELECT中有几项,fetch from @cursor_name into @cust_id就应该声明几个变量,而且顺序和类型必须一致.*/
declare @cursor_name cursor,
@select_command varchar(8000),
@cust_id varchar(20)
select @select_command = 'select cust_id from so_cust'
execute usp_createcursor @select_command,@cursor_name OUTPUT
fetch from @cursor_name into @cust_id
while @@fetch_status = 0
begin
fetch from @cursor_name into @cust_id
end
close @cursor_name
deallocate cursor_name

说明:上述代码在MSS SQL SERVER7.0上通过。其它数据库只需修改一下抓取栏位及其类型的系统表就可以了。


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